Figure MCA-1 shows the general structure of a system with these operations. The memory might be organized in one of the following ways:
1. Linearly-unordered - Each time a new entry name is to be written into the memory, it is appended to the existing list as an entry name - data pair. Figure MCA-2 shows such a memory organization.
2. Linearly-ordered - Each time that a new entry name is to be written into the memory, it is added so that the entry names appear in some fixed order. The same entry name-data pair could be used as in Figure MCA 2, except that the entry names would be ordered. The simplest scheme for entering data in an ordered list is to find the proper place for the entry name-data pair, then move all entries which appear after the new entry down two spaces in memory and add the new data.
Fig.. MCA-l. PMS diagram of the general structure of an M(content addressable).
3. Linked-list - If ordered entry names are desired but the moving required in the previous case is not allowable, then a linked list structure might be feasible. Associated with each entry name-data pair is a link which points to the next entry in the list. The link most likely to be used is the physical memory address. Adding a new entry involves stepping through the linked list to find the proper location, entering the new entry at an available memory location, setting the link of the new entry to have the value of the link of its predecessor, then changing the link of the predecessor so that it points to the new entry. Deleting an entry simply involves setting the link of the predecessor to the value of the link of the entry that is to be deleted. Figure MCA-3 shows an example of a linked list, organized memory.
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